1. Field of the Invention
The present invention relates generally to the field of integrated devices, and more particularly to a method for integrating at least one micro electro mechanical system (MEMS) device with one or more complementary metal oxide semiconductor (CMOS) devices.
2. Description of the Prior Art
A micro electro mechanical system (MEMS) is a tiny device with both electronic and mechanical functions. The MEMS can include accelerometers, gyroscope, magnetic sensors, pressure sensors, microphones, humidity sensors, temperature sensors, chemical sensors, biosensors, inertial sensors, as well as other well known MEMS common utilizations. In the past decades, the MEMS have been further integrated with CMOS such that integrated microelectronics including both MEMS and CMOS can be obtained.
Along with the progress in the semiconductor industry, research and development in integrated microelectronics have continued to produce astounding progress in the CMOS and the MEMS technologies. The MEMS, however, continue to rely upon conventional process technologies. In layman's terms, the microelectronic ICs are the “brains” of an integrated device that provide the decision-making capabilities, whereas the MEMS are the “eyes” and “arms” that provide the ability to sense and control the environment. Some examples of the widespread application of these technologies are switches in radio frequency (RF) antenna systems and accelerometers in sensor-equipped game devices. Though they are not always easily identifiable, these technologies are becoming ever more prevalent in society every day.
Although highly successful, the ICs and in particular the MEMS still have limitations. With the continuous reduction of the size of the MEMS, the residual stress gradient existing in the layers of the MEMS has become more predominant and often causes vertical curling in the sub-structures of the MEMS. For example, MEMS may be a multi-layered structure made of several metal layers, such as Al and TiN, and dielectric layers, such as SiO2. Due to different thermal expansion coefficients (TEC) of metals and dielectric materials, during the fabrication process for the integrated microelectronics, stresses may be generated and accumulated on the interfaces among the metal layers and/or the dielectric layers. This phenomenon causes serious deformation of the MEMS and inevitably reduces the reliability of the corresponding integrated microelectronics. Consequently, how to avoid the deformation of the MEMS is still an important issue in the field, in order to improve the performances of the corresponding integrated microelectronics.